Analysis with solid phase reagent carriers

Solid-phase chemistry is a category of analytical techniques characterized by three features: dry reagents fixed on or in an inert carrier; they are transformed into a liquid state of reactivity solely by fluid from the sample, movement of fluid in the carrier happens through capillary surface forces. A number of industrial laboratories have adapted these technologies to a majority of parameters of blood or serum respectively. The most frequently used measuring devices are new developed reflectometers; in one system (Ektachem) disposable ion selective electrodes have been newly developed in addition. The most important systems on the market are Ektachem (Kodak), Reflotron (Boehringer, Mannheim) and Seralyzer (Ames). These systems differ with respect to the construction of the reagent carriers and of the reflectometers. Solid-phase chemistry has the following advantages over the conventional analytical techniques: The sample volume is small, and the instrumentation is not complicated. The reagents are ready for use, and one system permits the use of whole blood without centrifugation. In this way it is possible to perform decentralized analyses at the patient's bedside, or in the physician's office. The disadvantages are the complete dependency of the user on the manufacturer with respect to the methodology and the quality of the reagents and instrumentation, the relative high price of the test-elements, and the limited possibility for the processing of long series. Additional problems are associated with quality control and drug interference. Nevertheless it can be expected that in the future increasing numbers of clinical chemical analyses will be performed by solid-phase chemistry, especially in general practice.